Optimizing Positronium Rydberg manipulation

In recent experiments we showed how we successfully manipulated the trajectories of Rydberg Positronium atoms using electric field inside a curved quadrupole guide, which allows us to perform velocity selection on the Positronium atoms that enter the quadrupole field.

These curved guide experiments were performed by exciting Positronium to n = 14, which is a state that has a relatively low mean lifetime of ~8 \mus, which is comparable to the flight time of our experiment, meaning that many of the n = 14 atoms undergo radiative decay before they can be detected. However, when judging what the most efficient n for guiding is, we need to have into consideration a few other factors. The lifetime of different n states goes up as n^3, but the field-ionisation rate goes up as ~n^{-4}, and the dipole moment as n^2. Combining all of these factors and implementing them into trajectory-simulations based on the electric fields generated by the curved guide, we were able to determine that the most efficient n for curved guiding is n = 14, as it can be seen from the graph below.

These simulations agree with our data and were instrumental in determining the optimum parameters of the experiment.

We are currently working on implementing this off-axis curved guide into a scattering experiment using helium ions, below you can see at the bottom of the image the new scattering chamber that has been coupled to the Positronium Rydberg beam.

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